The present invention relates to an autonomous mobile robot, preferably a robot for cleaning, and a system of control of a robot able to guide it towards a fixed station and/or able to adapt its behavior to the local degree of dirtiness and/or comprising a rotary brush and able to release the robot after the blocking of the aforementioned brush.
The invention relates more particularly to a system of guidance of the path of an autonomous mobile robot, including its positioning with respect to, and the approach towards, a fixed station of recharge in energy or discharge of elements collected by the robot. It will be, most frequently but not exclusively, a robot for cleaning the ground, which is provided with rechargeable batteries, for example a robotic vacuum cleaner. However it can also be a robot for spreading a substance or a monitoring robot.
An autonomous mobile robot, for example supplied with batteries, presents a limited autonomy. If one wants to obtain a continuous operation, the robot must be able to recharge its batteries at regular intervals of time. Other functions can also require the regular access to a fixed point for example the unloading of a bag of dust (robot-like vacuum cleaner) or re-supplying in fuel (thermal engine) or in a product to be spread.
A solution to this problem has already been disclosed (see EP-A-0744093), where in the mobile machine, sensitive to the gradient of an electromagnetic field, repositions itself automatically to the vertical of a coil traversed by a AC current.
In the case of surfaces comprising disturbing elements for the electromagnetic field (steel reinforcement of concrete for example), the above system operates with difficulty.
It can then be preferable to associate with the fixed station an infra-red radiation source (transmitting LED) allowing the mobile machine to locate the station remotely.
U.S. Pat. No. 4,679,152 discloses an autonomous mobile robot able to automatically return to a recharging station when the level of charge of a battery decrease below a predetermined threshold. The recharging station and the mobile robot are provided with a infra-read beam transmitter and a system of detection connected to a microcomputer. The robot and the recharging station may thus communicate in a bi-directional way. There is provided a search program with an opto-acoustic system which may involve a random moving of the robot on the work surface. Such system is complicated and appears to be poorly efficient when a very accurate positioning of the robot relative to the recharging station is required for the recharging operation. The purpose of the present invention is to overcome this drawback by providing, according to the simplest embodiment, a system using a narrow beam emitted by the recharging station, detectable by a directional sensor located on the chassis at the center of rotation of the robot.
According to a first aspect of the invention, a relatively narrow beam, varying for example between 2 and 10xc2x0 preferably approximately 5xc2x0, emerges from the fixed station. The corresponding transmitter and the associated station are preferably oriented so that the beam extends over a maximum length of the work surface of the robot. The mobile robot, provided with a system of directional detection of infra-red emission, is moving substantially in a random way on this surface, crosses and detects the narrow beam in statistically periodic manner.
According to a preferred embodiment, if some duration of work is exceeded, e.g. 15 to 45 minutes, whatever the state of load of the battery, the robot will return towards the fixed station for a cycle of recharge or refill as soon as it crosses an infra-red beam of a given intensity. If it is near the station after the above-mentioned duration of work, it will join it and will thus start a reload. This process avoids the operation of seeking the beam when the state of the battery decreases below a predetermined level. The narrowness of the beam allows a precise final positioning relative to the fixed station, and thus allows, for example, a recharging operation by induction or more simply by physical contact of conductors.
As the working time increases, the algorithm of the microprocessor performs so that the threshold of intensity of the infra-red beam to be detected by the mobile robot decrease in a linear way or by increment, in order to initiate the return step.
The stage of return can cause the discontinuance of all the functions of the robot which are not essential in order to find the station of recharge or refill.
According to another embodiment of the invention, the system of guidance and of positioning is based upon at least two beams of different directionality property emerging from the fixed station, the beam(s) less directional being used for the approach towards the fixed station, while the more directional beam is used for the ultimate stage of precise positioning of the robot relative to this fixed station. This alternative allows the guidance of the robot in a more complex environment (e.g. an apartment with several rooms, with several doors).
The transmitter of the less directional beam is located at a level of the fixed station so that its influence decreases at the ultimate stage of approach and of positioning of the robot. It can be manually directed as desired and located at the end of an overhanging arm above the front part of the fixed station itself.
In the phase of positioning, the transmitter will thus be advantageously located above the robot, the beam emitted being then out of the detection plane of the sensors of the robot. The latter, by a movement of rotation around its center, is then able to determine a final position of recharge, for example with physical contact, while basing itself on the signal of the transmitter of stronger directionality located in the detection plane of the sensors of the robot. The power of the beams can be different, the most powerful beam being generally but not necessarily the least directional beam.
The robot includes a directional system of detection of infra-red emission, for example comprising at least two directional sensors for which intensities of signals are compared, in a known way, by a microcomputer to control a rotation towards the source of emission. These sensors are preferentially located on the chassis at the center of the robot, oriented in the direction of movement of the robot. Possibly, one or several other sensors may be provided, for example on the lateral sides or on the rear side, advantageously having directional detection system substantially opposed to that of the central sensors. Advantageously also, the beams to be recognized by the sensors of the robot will be modulated in order to avoid any background noise.
According to this aspect of the invention, there is proposed a system of location and positioning relative to a fixed station for an autonomous mobile robot moving in a room characterized in that the fixed station emits two modulated infra-red beams, primarily in the plane of the rooms, one of the beams being appreciably more directional than the other. The least directional transmitter beam allows the location and the approach of the fixed station by the mobile robot provided with directional sensors sensitive to these beams. The signals of the sensors are treated by one microcomputer controlling the advance of the mobile robot, the transmitter of weaker directionality being located on the fixed station at a position perpendicular to the mobile robot when the latter joins its desired position in the fixed station, the more directional beam is then able to be detected in a more sensitive way by the aforementioned sensors, precise positioning being carried out by rotation of the machine about a vertical axis according to an algorithm based on the detection of the narrow beam.
According to an alternative one proposes a system of location and of positioning at a fixed station for a mobile autonomous robot moving in a room characterized in that the fixed station emits at least three infra-red modulated beams, one of the beams being appreciably more directional than the others. Transmitters of the least directional beam, and generally moreover stronger intensity, allows the location and the approach to the fixed station by the mobile robot carrying the directional sensors directional sensitive to the known as beams. Signals from the sensors are treated by a microcomputer controlling the advance of the mobile robot, the transmitters of less directionality being oriented and being located on the fixed station such that the beams cross each other in the immediate vicinity of the station. The most directional beam, which can be of lesser intensity, is then able to be more easily detected by the aforementioned sensors, precise positioning being carried out by rotation of the machine around a vertical axis according to an algorithm based on the detection of the narrow beam.
According to still another embodiment, the modulation of the beams emitted by the fixed station, including then a microcomputer, can transmit information to the robot, or to one robot among others if several robots are used with the same central station. This information can refer to availability of the station for a recharge operation an/or discharge, or can constitute an instruction relating to the working method, or to stopping or recall of the robot, sound localization of the robot etc. Possibly one can also envisage a transmission in return towards the fixed station, with the assistance of an infra-red transmitter carried by the robot.
The present invention also relates to a technique of guidance for the vacuum-cleaning of ground of dust, applicable to the autonomous robots used for cleaning.
Document EP-A-0769923 discloses a mobile autonomous machine for the vacuum-cleaning of ground, of low power and of small size allowing it to cover easily a surface encumbered by, for example, pieces of furniture.
The recharge of the batteries of the robot is advantageously coupled with the discharge of accumulated dust.
The content of the above-mentioned document is incorporated by reference in the present description.
The low power of this suction robot does not always allow however to carry out a thorough cleaning in only one passage. It can thus be necessary when the machine is over a particularly dirty surface, to envisage a longer time of passage (for example passing from a velocity of 20 cm/sec to 10 cm/sec) and/or to have additional passages to clean surface completely.
To this end, according to another aspect of the invention, a particular technique of cleaning is provided, such technique being applicable to any autonomous robot used for vacuum-cleaning and/or brushing.
The technique of guidance for the cleaning of ground by a robotic vacuum cleaner is indeed characterized in that the path followed by the robot depends on the quantity of particles present on the surface to clean, the aforementioned quantity being estimated by an analyzer of particles located near the opening of suction, or in one cavity of brushing of the robot, the aforementioned analyzer sending signals to a microcomputer carried by the mobile robot and controlling the displacement of the robot according to the said signals.
In addition, the aforementioned analyzer of particles can have the function of determining the degree of filling of the dust tank. If dust accumulates beyond a certain point the same infra-red beam located after the suction opening, that is to say at the level of the tank preceding the filter, will be stopped, which the microcomputer will interpret as a corresponding signal.
According to the measured quantity of aspired dust, the microcomputer can for example control one deceleration and/or a linear forth and back movement of the mobile robot.
The microcomputer can also control a movement of systematic cleaning, for example a forth and back movement in fan order.
Advantageously the microcomputer can take into account the size of the particles and their number, according to the amplitude and the frequency of the signals emitted by the analyzer of particles. An analysis of the type of dust collected, thanks to the knowledge of the size of the grains and of their number, makes it possible to refine the robots, behavior by correcting its path, the number of revolutions of the brush and/or the power of the vacuum cleaner turbine.
The analyzer of dust comprises for example a transmitter and a receiver, preferably in the infra-red.
The microcomputer can advantageously keep in memory a global average of the level of dust detected by the sensor of dust on a long distance, the activation of a particular cleaning algorithm taking account of the aforementioned average.
Moreover, advantageously, the suction robot can include a sensor of dust wherein one or several elements are periodically or constantly automatically cleaned by a flow of air oriented towards its surface.
According to another aspect of this invention the autonomous robot is a robot including a rotary brush.
The invention thus proposes a surface cleaning robot comprising as element of cleaning at least a rotary brush, and comprising a microcomputer controlling at least, via an algorithm, the velocity and/or the path of the robot characterized in that the microcomputer is associated with an algorithm which take account, to determine the aforementioned speed and/or the aforementioned path, of at least of the rotational velocity of the aforementioned rotary brush. The robot for cleaning is typically a robotic vacuum-cleaner.
Advantageously, the microcomputer of the robotic vacuum-cleaner takes account, in order to determine the power of aspiration, of the rotational speed of the aforementioned rotary brush. The suction power can inter alia be dependent on the number of revolutions of the aforementioned brush.
The microcomputer is therefore able to take account of the measurement of number of revolutions of the motor to determine the behavior of the aforesaid robot.
The presence of a rotary brush presents however the disadvantage of seeing the brush blocking itself when it meets, for example, the fringes of a carpet laid out on the surface to clean.
A solution with this problem was described in the patent application PCT WO 97/40734 and consists in reversing the direction of rotation of the brush so as to release it.
The solution of the present application has the advantage of not requiring a precise control of the brush, nor the inversion of its way of rotation. This simplifies the design of the robot. This more simple solution appeared to be more effective in practice.
The device according to the invention includes a system comprising a rotary brushxe2x80x94driven by a motorxe2x80x94activated by microcontroller (or microcomputer) controlling the whole of the functions of the autonomous robot. Reference is made in this respect at the patent application PCT WO 96/01072 incorporated herein by reference.
The number of revolutions of the brush is analyzed by the microcontroller, preferably constantly.
This measurement can be carried out according to several known techniques (measurement of the consumed current by the motor in the case of a dc motor, measurement of frequency of the impulses in the case of a motor without brushes, optical coder).
The measurement of this number of revolutions allows the microcontroller to deduce certain information concerning, for example, the nature of the cleaned surface or the occurrence of an incident and to adapt the robot""s behavior consequently.
At the time of occurrence of an incident such as the halt of the rotary brush, caused for example by the rolling up of fringes of a carpet around the axis of the brush, the microcontroller will disconnect the brush and will cause the robot to start a series of operations of disengagement.
This operation can be, according to the design of the robot, one mechanical disengagement but will be preferably an electric disconnection of the motor.
As an example some particularly efficient maneuvers are described hereafter.
The robot moves back of a distance equal to its diameter (brushes disconnected). By doing this the fringes exert one effort of unfolding on the axis of the brush which is in free wheel.
The brush is released. The retreat brings the robot outwards of the zone of the fringe. The robot rotates then while re-engaging the brush. If, at this stage, the brush is still blocked, it stops its rotational movement and the robot performs a new retreat to again attempt to permit the rotation of the brush and so on until the brush is released.
The maximum number of reiterations is fixed by the program and by the maximum free distance for retreat of the robot.
If this maximum distance is reached without the brush being released, the robot will continue the iterations but in forward motion.
If no operation succeeds in releasing the brush, the robot is put in a waiting status associated to a signal, and a manual intervention is necessary.
Advantageously, the analysis of the number of revolutions of the brush also makes it possible to know the nature of the ground cleaned.
A high number of revolutions reflects a smooth ground, a slower speed reflects a surface covered with a carpet. The slower the speed, the thicker the carpet. This analysis allows the robot to adapt its velocity in advance and to adapt the suction power according to the nature of the ground to be cleaned.
The invention can be applied to cleaning robots other than vacuum cleaners, for example to robots for cleaning unspecified surfaces with liquids or to robots to wax parquet floors.
The invention thus relates also to a cleaning robot comprising a rotary brush and a microcomputer, a means for detecting the blocking of the rotary brush which is associated to the microcomputer, an algorithm of disengagement of the robot, a means of disengaging the rotary brush relative to the associated motor, the algorithm including causing a movement of retreat of the robot followed by a rotation and the resumption of the forward movement of the robot.
The means of disengagement consists advantageously in a disconnection of the motor from its electrical supply.
In short, the robot for cleaning a surface according to one aspect of the invention comprises at least a rotary brush, the speed and/or the path and/or possibly the suction power of a turbine, being dependent on the revolution speed of the aforementioned rotary brush.
For a robotic vacuum-cleaner, in particular a domestic one, the rotational movement of the brush takes place preferably in a vertical plane relative to the surface to be cleaned.
The invention relates also to method of operation of a cleaning robot as above-mentioned, the blocking of the rotary brush being detected by the aforementioned microcomputer which controls then an operation for releasing the robot. The aforementioned releasing operation comprises at least a disengagement of the said rotary brush relative to the motor operating it, coupled to a movement of retreat of the robot followed by a rotation and the resumption of the forward moving of the robot. The operation possibly includes several cycles of disengaging-retreat-rotation-forward movement.
According to still another aspect of the invention, which can be applied to any autonomous mobile robot, more advantageously to robots of great dimension (p.e. 80 to 250 cm), the robot comprises a linear sensor of collision surrounding entirely or partly the lower portion of the careenage in the plane of movement. The sensor is made of a metallic linear conductor and, in parallel, a linear plastic conductor element, for example made out of conducting rubber. The unit can be included in a sheath or an insulating flexible membrane fixed along the edge of body. For example, the linear elements are fixed by gluing two internal opposite faces of the sheath. These two elements are separated by a small distance. The ends of the conducting plastic are subjected to a potential difference, for example of 5 volt, that is to say 0 volt at an end and 5 volt at the other end. At the occurrence of a collision of the robot with a frontal or lateral obstacle, one of the two elements is able to come elastically into contact with the other element under the effect of a temporary pressure resulting from the impact of the robot with the obstacle. It will be understood that the instantaneous voltage on the conducting element is a function of the distance from the point of impact to one of the end of conducting plastic, which has a higher resistance. Thus a measured voltage of 2,5 volt means that the impact took place roughly at the middle of the linear sensor. The measured voltage at the level of the conducting element thus constitute a signal sent to the microcomputer in order to locate the point of impact at the basis of careenage.
The improvements according to the invention are to be applied more particularly to mobile robots moving, in their mode of normal operation, in a random way without any system of precise positioning.